A new paper from NIEHS-funded researchers found an association between low-level prenatal mercury exposure and increased risk of attention-deficit/hyperactivity disorder (ADHD)-related behaviors in children. However, consuming more than two serving of fish per week was linked with a lower risk for ADHD-related behaviors.

The researchers studied children born in New Bedford, Mass. They conducted neuropsychological assessments for children at age 8 who had peripartum maternal hair mercury measures (421 children) or maternal reporting of fish consumption during pregnancy (515 children). The mothers’ median hair mercury level was 0.45 micrograms per gram (mg/g) (range = 0.03 to 5.14 mg/g), and 52 percent of them consumed more than two servings of fish a week. Multivariable regression models showed that mercury exposure was associated with inattention and impulsivity/hyperactivity. Associations between mercury and behavior were detected primarily for boys. However, when the mothers consumed more than two servings of fish per week, there was a protective effect for ADHD-related behaviors, particularly impulsive/hyperactive behaviors (relative risk = 0.4; 95% CI, 0.2-0.6).

The author of a related editorial says that the study’s findings point to the need for a national scientific advisory panel to evaluate environmental influences of ADHD and that new evidence linking environmental contaminants with ADHD reinforces the urgency of revising the regulatory framework for environmental contaminants and toxicants.